Conventional wafer etching machines include concentric inner and outer rings that secure a wafer in place over an electrode. The outer ring may be placed in the machine in only one orientation and is typically fabricated of stainless steel. The inner ring is often manufactured of a ceramic material and includes a plurality of radially extending fingers. The fingers engage and apply pressure to a substantially circular wafer to hold the wafer in place on the electrode. Occasionally, the rings must be removed from the machine and cleaned.
Once the rings are removed from the machine, there are no markers on either the machine or the rings to aid with the reinstallation of same. Technicians often use the "eyeball" method to visually align the rings with one another and with the machine. Another technique, involves using a straight edge to align the inner and outer rings and to orient the outer ring with the machine. These methods often result in ring alignment errors.
Evidence of errors resulting from improperly aligned rings may not appear for several hours after reinstallation of the rings. Typical alignment errors include improper seating of the outer ring in the machine or repeated attempts to align the ring properly with the machine. With respect to the inner ring, if all but one of the fingers of the inner ring do not engage the wafer, the wafer may be improperly seated over the electrode, resulting in improper etching of the wafer. All wafers improperly etched due to the misalignment must be discarded or reworked, resulting in increased production cost and time.
In addition to increased production cost, imprecise alignment methods result in prolonged maintenance periods. It generally requires approximately two hours of machine downtime to correcting misalignment problems. Consequently, a tool is needed that will permit proper alignment of the rings and orientation of the outer ring prior to their installation in the machine.